1. Field
The proposed device relates to the field of seismic prospecting of mineral deposits, more precisely, the excitation of seismic waves in the ground when conducting seismic exploratory work.
2. Description of Related Art
A device is known for exciting seismic vibrations (see Shneyerson, M. B. et al., Nazemnaya seysmorazvedka dlya vozbuzhdeniya seysmicheskikh kolebaniy (Land-based seismic prospecting with nonexplosive vibration sources), M: Nedra, p. 85), including a bushing with rod situated in a central channel of a piston, forming with the bushing a working chamber and a damping cavity. The pressure impulse in the working chamber of the device is formed by discharging into it a portion of air compressed to a pressure of 15.0 to 16.0 MPa. As a result, the air pressure in the working chamber is instantaneously raised from 0 to 3.5-4.0 MPa. The bushing in this process acts on the ground, generating a seismic wave in it, while the piston rebounds upward. The drawback of this device is the substantial operating expenses related to the use of a low-efficiency and costly high-pressure compressor to form the working agent, compressed air, which is entirely released into the atmosphere after producing the force pulse.
These drawbacks are eliminated in the device for exciting seismic vibrations (see inventor's certificate SU No. 1728820 A1 23 Apr. 1992), which can be considered as the prior art. The device includes a rod and piston assembly, and a plate fastened to its lower end, wherein an axial through channel is made in the body of the rod and piston assembly, while the piston of the rod and piston assembly is placed in the body of a hydraulic cylinder equipped with an upper cap and separated from a lower pneumatic chamber in which the plate is situated by a partition; the plate is able to interact by its lower end, forming a pneumatic gripping device, with the upper end of a stepped cylindrical waveguide, whose upper step of larger diameter is located in the pneumatic chamber, while the lower step outfitted with a working plate at its lower end forms a damping cavity with the lower cap of the pneumatic chamber.
The drawback of this device for exciting seismic vibrations is the substantial length of the interval of time from the sending of the electrical signal to unseal the pneumatic gripping device until the time of dynamic action on the ground. This interval is not sufficiently stable to ensure a synchronized operation and it does not allow an operation with a group of seismic vibration sources and signal build-up. This, in turn, substantially lowers the working effectiveness and prevents the use of this device to study cross sections at the required depths. The great length of the above-indicated interval of time is explained by the fact that a portion of compressed air delivered by valve from the pneumatic system of the device is used here for unsealing of the pneumatic gripping device (pneumatic lock). But the length and volume of the air supply channel to the pneumatic lock (including the length of the axial through channel in the body of the rod and piston assembly) are large and their filling with compressed air from the pneumatic system is extremely long.